Implantable stimulation devices generate and deliver electrical stimuli to bodily nerves and tissues for the therapy of various biological disorders, such as: pacemakers to treat cardiac arrhythmia; defibrillators to treat cardiac fibrillation; cochlear stimulators to treat deafness; retinal stimulators to treat blindness; muscle stimulators to produce coordinated limb movement; spinal cord stimulators to treat chronic pain; cortical and deep brain stimulators to treat motor and psychological disorders; and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder sublaxation, etc. The present invention may find applicability in all such applications, although the description that follows will generally focus on the use of the invention within a spinal cord stimulation system, such as that disclosed in U.S. Pat. No. 6,516,227, issued Feb. 4, 2003 in the name of inventors Paul Meadows et al., which is incorporated herein by reference in its entirety.
Typical implantable stimulation devices include a neurostimulator, one or more leads electrically coupled to the neurostimulator, and an array of stimulator electrodes on each lead. The stimulator electrodes are in contact with or near the bodily tissue to be stimulated. A pulse generator in the neurostimulator generates electrical pulses that are delivered by the electrodes to bodily tissue. The neurostimulator typically includes an implantable rounded case having circuitry such as a printed circuit board, a telemetry coil for communicating with an external programmer to control the electrical pulses, and a charging coil for charging the neurostimulator.
The neurostimulator also includes a header having one or more connector assemblies for receiving the leads, wherein the connector assemblies have one or more connector contacts for coupling to the leads. In common models of such neurostimulators, there are two connector assemblies in the header, each having eight contacts. However, to allow for greater range in stimulation parameters, it is desirable for the header to include more electrode contacts for coupling to the lead, for example, thirty-two contacts. At the same time, it is preferred to keep the case and header as small as possible and to maintain a curved configuration for patient comfort. Therefore, a proper neurostimulator design to accommodate thirty-two electrodes, without affecting device performance, is desirable.
It is also common for neurostimulators to house a telemetry coil in the header. However, this requires a feedthrough to couple the telemetry coil to resonant circuit components and transceiver circuitry in the case. This can add to the complexity of the device and lead to problems with hermeticity. Additionally, the feedthroughs require significant extra steps during manufacture, thus allowing for greater error and quality concerns.
Another disadvantage of having the telemetry coil in the header is that the coil and the feedthroughs connected to the coil take up space in the header, which may be limited based on the complexity of the stimulation system. At the same time, it is desirable to make stimulation devices smaller for patient comfort. Moreover, while previous neurostimulators had eight or sixteen contacts for coupling to the electrode leads, newer designs may include thirty-two or more contacts, further limiting space in the header.
Thus, there remains a need for improved stimulation devices and methods that optimize performance with an increased number of electrodes and selective positioning of the telemetry coil, while also having a small, rounded configuration for patient comfort that does not compromise device performance.